The present invention relates to an ultrasonic wave generator, and in particular relates to the same according to the principle of the piezo electric oscillation.
Recently ultrasonic wave generators have been variously utilized in fields including sonar fish detection apparatuses, moisture suppliers, ink mist type printers, etc. Ink mist type printing is one of the most important fields to which the present invention may be applied. The ink mist type printer operates on the principle that an ion stream modulated by an aperture board according to the pattern of the character to be printed, charges the ink mist, which is then attracted by an electric field to the surface of the paper. The ink mist type printer has many advantages, among which are that any character, including even Chinese characters, can be printed, the printing speed is very high, and the process is noiseless. The present applicants have already filed some patent applications concerning the ink mist type printer, one of which being U.S. Ser. No. 492,340. In the ink mist type printer, an ink mist is generated as the result of an ultrasonic wave energy being applied to the ink. In order to obtain clearly printed characters, the density of the ink mist should be as high as possible, preferably almost at saturation point. To attain sufficient power or energy of the ultrasonic wave to meet this end an improved effective ultrasonic wave generator with low power loss is required.
A prior ultrasonic wave generator comprises an oscillator, a power amplifier for amplifying the output of the oscillator, and a piezo-electric transducer connected to the output of the power amplifier for generating ultrasonic wave energy. However, the resonant frequency of the transducer depends upon the quality of the raw material, the cutting accuracy, the mounting means and/or the change of the temperature. Further, the output frequency of the oscillator is affected by errors in circuit parts and/or the change of the temperature. Accordingly, in many cases the transducer does not match the oscillator, and therefore can not provide the maximum power of the ultrasonic wave.
As apparent from the above explanation, disadvantages of prior ultrasonic wave generators include the reduction of power of the ultrasonic wave due to mis-matching of the transducer and the oscillator.